Research On Distributed Narrowband Radar System

Radar imaging has gradually become the main trend of radar technology development.Traditional radar systems usually use wideband signals to improve the range accuracy.As the bandwidth of the signal increases,the radio spectrum resources become more and more tense,which brings great challenges to the design of radar systems.A narrowband imaging radar is studied in this thesis,which can effectively reduce the spectrum occupancy.Multi narrowband radars consist of distributed radar system,which can detect the target area in different angles.By combining the imaging results of several radars,the system can obtain more comprehensive imaging information,overcome the shortcomings of single radar and better meet the imaging needs.Therefore,it is of great significance to study distributed narrowband radar system.The thesis mainly studies the distributed narrowband radar system,respectively,from aspects of narrowband Doppler BP imaging algorithm,algorithm simulation,simulation error analysis,distributed narrowband imaging system building and small scale experiment system building.The thesis firstly analyzes the principle and process of the traditional time domain wideband BP imaging.Traditional methods rely on large bandwidth to provide high range resolution.Aiming at the problem of insufficient range resolution of narrowband signals,an imaging algorithm using echo Doppler resolution is proposed.The method realizes the target imaging by constructing imaging data and projecting each slow time sampling data back to the equal Doppler line.By analyzing the point spread function,it is concluded that the imaging rotation angle is the main factor affecting the imaging resolution.The imaging method does not depend on the bandwidth of radar transmit signal,so it needs larger observation angle to obtain the imaging resolution compared with wideband signal.The circle scanning simulation system is designed based on the turntable model,and the parameter settings of the image are analyzed.1.The cases of single target and multiple targets are respectively configured,and the target imaging results under different observation angles are summarized and analyzed.2.The model explores the feasibility of the imaging of the space target,and completes the imaging simulation of the spatial multi-point target.3.In practice,the radar platform does not always follow the ideal trajectory,so the error is added in different directions of the radar platform.The imaging under the presence of position errors is analyzed.The architecture of the distributed narrowband radar imaging system is designed,and the corresponding Doppler BP incoherent imaging method is proposed.Firstly,in the case of the ideal trajectory without errors,the distributed imaging is simulated by changing the number and trajectory of the target in the case of the point target and the area target.The results show that the distributed platform imaging can improve the two dimensional resolution uniformity of the imaging region,and make up for the limited observation angle of the single radar.Secondly,the internal angle error and radial position error model of distributed system are established.By introducing the position error between the relative motion angle and the circumferential radius of motion between radars,the imaging results of nonideal trajectories of radar are simulated.The experimental system of distributed narrowband continuous wave turntable imaging is designed.The data acquisition scheme is designed for single target and multi targets,and the measured data is imaged.In the model of radar moving along the circular trajectory,the effectiveness of the distributed narrowband continuous wave Doppler BP imaging algorithm is verified.